1. Scope of the Invention
The present invention relates to a special process for carrying out injection molding of plastic parts which have hollow or irregularly shaped forms as well as undercut regions. The invention also concerns the core member which is used for carrying out the method. 2. Description of Prior Art
Various methods using a destructable core for providing injection molded plastics parts which include hollow or undercut shapings are already known.
The difficulty of carrying out injection molding of such parts essentially resides in the accuracy of molding. The surface finish of the cores used must be excellent, and the core must not be able to become deformed at the actual time of injection.
One process which is known notably from French Pat. No. 1,366,921 consists of using cores in low melting point alloys. The disadvantages which are generally encountered when carrying out this process are as follows:
Since the melting point of the plastic material injected into the mold is greater than the melting point of the metal or the alloy of which the core is fabricated, balancing of the temperatures of the injected material and of the core presents a very significant obstacle to the usage of such a process.
The operation for recovering the core material by melting is a relatively slow process. It is necessary to reheat the complete core and injected plastic part combination at a temperature which must still be less than the melting point of the plastic material.